🔍 Improving: LMP, multiplying by 2

[eduherminio]

The alternative implementation failed in #1128 while using the same concept of #1127 (common formula, but that one also failed quickly).

Test  | search/improving-lmp-2
Elo   | 8.39 +- 4.48 (95%)
SPRT  | 8.0+0.08s Threads=1 Hash=32MB
LLR   | 2.90 (-2.25, 2.89) [0.00, 3.00]
Games | 10858: +3262 -3000 =4596
Penta | [276, 1245, 2196, 1365, 347]
https://openbench.lynx-chess.com/test/873/

Test  | search/improving-lmp-2
Elo   | 1.48 +- 3.59 (95%)
SPRT  | 40.0+0.40s Threads=1 Hash=128MB
LLR   | 2.91 (-2.25, 2.89) [-5.00, 0.00]
Games | 14566: +3826 -3764 =6976
Penta | [278, 1799, 3070, 1855, 281]
https://openbench.lynx-chess.com/test/874/